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Electrical Engineering Dictionary - part 187

volume plasmon

a volume polariton in a

plasma medium.

volume polariton

a polariton that propa-

gates in unbounded medium, also referred to
as a bulk mode, wave by 180 degrees.

volume scattering

the reflection of elec-

tromagnetic waves from a collection of par-
ticles or transitions in media properties dis-
tributed throughout a three-dimensional re-
gion. Particles may or may not be immersed
or imbedded in a dielectric medium. See also

surface scattering

volumetric scattering

See

volume

scattering

von Neumann architecture

a stored

program computer design in which data
and instructions are stored in the same
memory device and accessed similarly.
See also

Princeton architecture

See

single-instruction stream, single data stream

von Neumann, John

(1903–1957) Born:

Budapest, Hungary

von Neumann is best known for his role in

the development of the theory of stored pro-
gram flexible computers. He is honored by
the reference to von Neumann machines as a
theoretical class of computers. von Neumann
also invented the idea of game theory. As a
mathematician, von Neumann published sig-
nificant work on logic, the theory of rings,
operators, and set theory.

His work, The

Mathematical Foundations of Quantum Me-
chanics, was significant in the mathematical
justification of that field. von Neumann was a
brilliant mathematician and physicist whose
theoretical contributions are fundamental to
modern physics and electrical engineering.
He was the youngest member of the Institute
of Advanced Studies at Princeton, and did
important work on the Manhattan project.

voting circuit

a circuit that provides fault-

tolerance by comparing its inputs and taking
a majority vote in case of disagreement.

vowel diagram

the articulation of differ-

ent vowels is strongly based on the position
of the tongue, which can be high/low and
front/back. The diagram defined by these
two dimensions is called vowel diagram.

voxel

the 3-D analogue of a pixel; abbrevi-

ation of Volumetric Picture Element. Math-
ematically it is a point in 3-D space having
integer coordinates; concretely, it can also
be interpreted as a cube of unit size centered
about that point. See

pixel

voxel adjacency

one of three types of ad-

jacency relations defined on voxels:

1. 6-adjacency: two voxels are 6-adjacent

if they differ by 1 in one coordinate, the other
two coordinates being equal; equivalently,
the two unit cubes centered about these vox-
els have one face in common.

2. 18-adjacency: Two voxels are 18-adjacent
if they differ by 1 in one or two coordi-
nates, the remaining coordinates being equal;
equivalently, the two unit cubes centered
about these voxels have one face or one edge
in common.

3. 26-adjacency: Two voxels are 26-adjacent
if they differ by 1 in one, two, or three co-
ordinates, the remaining coordinates being
equal; equivalently, the two unit cubes cen-
tered about these voxels have one face, one
edge, or one vertex in common. In these def-
initions, the numbers 6, 18, and 26 refer to
the number of voxels that are adjacent to a
given voxel. See

pixel adjacency

voxel

VP-PAW

See

variable polarity plasma arc

See

VQ encoding

See

vector quantization

encoding

2000 by CRC Press LLC

VSAT

See

very small aperture terminal

VSI

See

voltage-source inverter

VSWR

See

voltage standing wave ratio

See

potential transformer

2000 by CRC Press LLC

wafer

a thin slice of semiconductor ma-

terial on which semiconductor devices are
made. Also called a slice or substrate.

wafer fab

the facility (building) in which

semiconductor devices are fabricated. Also
called a semiconductor fabrication facility.

wafer scale integration

most integrated

circuits are cut from a large slice of material
called a wafer. With wafer scale integration,
the entire slice of material is used to create a
complex circuit.

wafer sort

a preliminary electrical test of

each die while still on the wafer to eliminate
most of the bad die before they are assembled.

wait state

a bus cycle during which a CPU

waits for a response from a memory or input-
output device.

wall clock

a device providing the time of

day; contrast processor clock. Elapsed wall
clock time for a process does not correspond
with processor time because of time used in
system functions.

Walsh cover

mutually orthogonal se-

quences used in direct-sequence code divi-
sion multiple access, obtained from the rows
of a Hadamard matrix. See also

Hadamard

matrix

Walsh transform

See

Walsh–Hadamard

transform

Walsh–Hadamard transform (WHT)
a transform that uses a set of basis func-
tions containing values that are either

+1 or

−1, and are determined from the rows of
the Hadamard matrices. This has a modest

decorrelation capability and is simple to im-
plement.

Waltz filtering

also termed “Boolean con-

straint propagation”; a method of simplifying
certain tree-search problems. It was origi-
nally developed to solve the computer vision
problem of labeling each edge of a line draw-
ing in order to give a 3-D description of the
represented object.

WAN

See

wide-area network

Ward–Leonard drive

an adjustable volt-

age control drive system for the speed control
of DC machines, whereby variable voltage
is supplied to the armature, while maintain-
ing constant voltage across the shunt or sep-
arately excited fields. The variable voltage
is obtained from a motor-generator set. The
Ward–Leonard drive was frequently used in
elevators.

warm start

(1) reassumption, without

loss, of some processes of the system from
the point of detected fault.

(2) the restart of a computer operating

system without going through the power-on
(cold) boot process.

watchdog processor

a processor that ob-

serves some process and signals an alert if a
certain event happens or fails to happen.

watchdog timer

a simple timer circuitry

that keeps track of proper system functioning
on the basis of time analysis. If the timer is
not reset before it expires, a fault is signaled,
e.g., with an interrupt.

water resistivity

a measure of the purity

of cooling liquid for a power tube, typically
measured in megohms per centimeter.

water tree

a microscopic cracking pattern

which forms in the insulation of cables which
are immersed in water or direct-buried in the
earth. See

tree

2000 by CRC Press LLC

watercourse

a line on a surface

f (x, y)

which represents a watershed of the inverted
surface

−f (x, y). The line of steepest de-

scent from a saddle point to a minimum is a
watercourse. Watercourses meet watersheds
at saddle points.

watershed

a line on a surface

f (x, y),

typically an image, which divides it into
“catchment areas.” Within a catchment area,
lines of descent all connect to the same mini-
mum point. The line of steepest ascent from
a saddle point to a maximum is a watershed.
Watersheds often correspond to ridges.

Watson, Thomas J., Jr.

Watson is best

known as the president of IBM who led the
company into a dominant position in the com-
puter industry. Watson took over his father’s
company, changed the structure, and moved
the company away from the card tabulating
business in which they held a dominant posi-
tion. Watson Jr. oversaw the development of
the IBM System/360 machines, which were
to give the company a dominant position in
computing.

Watson, Thomas J., Sr.

(1874–1956)

Born: Cambell, New York, U.S.A.

Watson is best known as the president

of IBM (International Business Machines).
While Watson was not a technical person, his
position as head of IBM put him in a position
of supporting the development of a number
of devices, both electronic and mechanical,
leading to the development of the modern
computer industry.

Watson-Watt, Robert Alexander

(1892–

1973) Born: Brechin, Angus, Great Britain

Watson-Watt is most famous for his pi-

oneering work in the development of radar.
Watson-Watt’s work is based on the princi-
ples elucidated by Faraday, Maxwell, and
Hertz.

A German physicist, Christian

Hulsmeyer had filed a patent in 1904 for an
earlier device. Lack of enthusiasm from the
German government and the governments in
France and the United States gave the En-

glish, who supported Watson-Watt, a clear
edge in this field.

Watson-Watt filed his

patent application in 1919. His device proved
invaluable to the Allies in World War II.

watt

unit of power in the SI system of

units.

Watt, James

(1736–1819) Born: Green-

ock, Scotland, U.K.

Watt is best known for his work in the de-

velopment of efficient steam power. Watt
began his career as an instrument maker.
When asked to fix a troublesome Newcomen
engine, he began to make improvements.
Watt eventually partnered with industrialist
Matthew Boulton to form a steam engine
company. Watt is credited with having de-
vised the horsepower system. The unit of
power, the watt, is named in his honor.

watt-VAR meter

meter capable of si-

multaneously measuring the real and reactive
power delivered to an AC load.

wattmeter

an instrument for measuring

electric power in watts.

A wattmeter re-

quires connections to measure both the cur-
rent through and the voltage across the load
being measured.

wave equation

equation governing the

evolution of a wave; in electromagnetics any
of several equations or equation sets starting
from the most general, nonlinear multivari-
able differential Maxwell–Heaviside equa-
tions and ranging down to the simplest first-
order rate equations.

wave impedance

the ratio of the trans-

verse electric and magnetic fields inside a
waveguide.

wave optics

formalism for optics in which

the fields are represented as wave phenom-
ena, in contrast to other ray or particle optics
models.

2000 by CRC Press LLC

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